The present invention relates to optical sensors and, more particularly, to optical sensors using heterodyne optical interferometry to implement confocal microscopy.
Well known works that use heterodyne interferometry to make birefringence measurements are described in J. Mackey, et.al., Meas. Sci. Technol. 10(1999) 946–955; B. Wang, e.al., U.S. Pat. No. 6,473,179B1, Oct. 29, 2002; F. Modine, et.al, Applied Optics, 14,3, March 1975; B. Wang, Optical Engg., 41,5, May 2002; B. Wang, Rev. Scientific Instru. Vol. 70,10, October 1999; H. Kowa, et.al., U.S. Pat. No. 6,157,448, Dec. 5, 2000; A. Ajji,et.al, U.S. Pat. No. 5,864,403, Jan. 26, 1999; C. Chou et.al, J. Opt. Soc. Amer. A, 14,6, June 1997; C. Chou, et.al, Applied Optics, 42,24, Sep. 1, 2003.
Works in heterodyne confocal microscopy include L-C Peng, et.al., Optics Lett., Vol. 26,6, March 2001. Works in confocal polarization microscopy include J. Bueno, et.al., Optics Lett., Vol. 27, No. 10, May 15, 2002; L. Yang, et.al., Applied optics, Vol. 42,28, 1 Oct., 2003; H. King, et.al. Optics Lett., 18,22, Nov. 15, 1993; P. Gleyzes, et.al., Optics Lett., 22,20, Oct. 15, 1997.
Works in spectral interferometry include: M. Raab et.al., J. Opt. Soc. Am. B, Vol. 2,9, September 1985; M. Shlyagin, et.al, Optics Lett., 20,8, Apr. 15, 1995; T. Fukano et.al., Optics Lett., 25,8, Apr. 15, 2000; Y. Watanabe et.al., Applied Optics, 41,13, 1 May 2002; C. Hitzenberger, et.al., Optics Express, 9,13, Dec. 17 2001; A. Vakhtin et.al, Applied optics, 42,34, 1 Dec. 2003; M. Choma et.al., Optics Express, 11,18, 8 Sept., 2003; R. Leitgeb, et.al., Optics Express, 11,8, 21 Apr. 2003; J. de Boer, et.al., Optics Lett., Vo. 28, No. 21, Nov. 1, 2003; S. Yun, et.al., Optics Express, Vol. 22, 11, 3 Nov., 2003; G. Hausler et.al., J. Biomedical Optics, 3,1, January 1998; R. Leitgeb, et.al, Optics Express, 11,23, 17 Nov. 2003; A. Fercher et.al., Optics Comm., 117, 43–48, 15 May 1995.
Earlier, for example, acousto-optic deflectors or Bragg cells using isotropic Bragg diffraction have been used to form scanning heterodyne interferometers such as in N. A. Riza, “Scanning heterodyne acousto-optical interferometers,” U.S. Pat. No. 5,694,216, Dec. 2, 1997; N. A. Riza, “In-Line Acousto-Optic Architectures for Holographic Interferometry and Sensing,” OSA Topical Meeting on Holography Digest, pp. 13–16, Boston, May, 1996; N. A. Riza, “Scanning heterodyne optical interferometers,” Review of Scientific Instruments, American Institute of Physics Journal, Vol. 67, pp. 2466–2476 7, Jul. 1996; and N. A. Riza and Muzamil A. Arain, “Angstrom-range optical path-length measurement with a high-speed scanning heterodyne optical interferometer,” Applied Optics, OT, Vo. 42, No. 13, pp. 2341–2345, 1 May 2003. These interferometers use the changing RF (radio frequency) of the AOD or isotropic Bragg cell drive to cause a one dimensional (1-D) scanning beam but perform optimally only for a given design wavelength.